The present invention is directly related to and is an improvement of the tap-off base assembly disclosed in U.S. Pat. No. 4,714,431, issued Dec. 22, 1987 and U.S. Pat. No. 5,192,217 issued Mar. 9, 1993. The tap-off base assemblies of U.S. Pat. Nos. 4,714,431 and 5,192,217 are directly associated with the electrical distribution systems disclosed in U.S. Pat. Nos. 4,673,229 issued Jun. 16, 1987 and 4,820,177 issued Apr. 11, 1989. Each of the previously referenced patents are assigned to the same assignee as the present invention and are incorporated by reference for the description of common features and applications.
It is common in the art of electrical busway distribution systems to include provisions for the installation of tap-off units at intervals along the busway housing. These provisions generally include a number of tap-off openings spaced at set intervals along the busway housing whereby access to the conductors enclosed within the housing is obtained. Each tap-off opening requires a tap-off base assembly. The tap-off base assembly includes a base, generally molded from an electrically insulating material, and a door. The tap-off base provides support for the conductors enclosed within the housing and includes a number of access openings through which the electrical connection of a tap-off device is made. The door provides a means for closing the access openings when a tap-off unit is not installed on the base. The door, when properly latched in the closed position, will prevent unintentional finger contact with the conductors inside the busway housing. A base as described and claimed in U.S. Pat. No. 5,192,431 will also prevent unintentional finger contact with the conductors while the door is in the open position. Both the door and base described above will provide an rating of IP-2X, as defined in IEC 529. The IP-2X rating, however, does not address the ingress of objects smaller than 12.5 mm or the ingress of water. In many applications it is required that other foreign objects smaller than 12.5 mm and water must be prevented from entering the busway housing.